node-red-nodes/parsers/smaz/smaz.js

// Copyright (c) 2006-2009, Salvatore Sanfilippo
// All rights reserved.

// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

//    * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
//    * Neither the name of Smaz nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Our compression codebook
 var rc = [
 " ", "the", "e", "t", "a", "of", "o", "and", "i", "n", "s", "e ", "r", " th", " t", "in", "he", "th", "h", "he ", "to", "\r\n", "l", "s ", "d", " a", "an","er", "c", " o", "d ", "on", " of", "re", "of ", "t ", ", ", "is", "u", "at", "   ", "n ", "or", "which", "f", "m", "as", "it", "that", "\n", "was", "en", "  ", " w", "es", " an", " i", "\r", "f ", "g", "p", "nd", " s", "nd ", "ed ", "w", "ed", "http://", "for", "te", "ing", "y ", "The", " c", "ti", "r ", "his", "st", " in", "ar", "nt", ",", " to", "y", "ng", " h", "with", "le", "al", "to ", "b", "ou", "be", "were", " b", "se", "o ", "ent", "ha", "ng ", "their", "\"", "hi", "from", " f", "in ", "de", "ion", "me", "v", ".", "ve", "all", "re ", "ri", "ro", "is ", "co", "f t", "are", "ea", ". ", "her", " m", "er ", " p", "es ", "by", "they", "di", "ra", "ic", "not", "s, ", "d t", "at ", "ce", "la", "h ", "ne", "as ", "tio", "on ", "n t", "io", "we", " a ", "om", ", a", "s o", "ur", "li", "ll", "ch", "had", "this", "e t", "g ", "e\r\n", " wh", "ere", " co", "e o", "a ", "us", " d", "ss", "\n\r\n", "\r\n\r", "=\"", " be", " e", "s a", "ma", "one", "t t", "or ", "but", "el", "so", "l ", "e s", "s,", "no", "ter", " wa", "iv", "ho", "e a", " r", "hat", "s t", "ns", "ch ", "wh", "tr", "ut", "/", "have", "ly ", "ta", " ha", " on", "tha", "-", " l", "ati", "en ", "pe", " re", "there", "ass", "si", " fo", "wa", "ec", "our", "who", "its", "z", "fo", "rs", ">", "ot", "un", "<", "im", "th ", "nc", "ate", "><", "ver", "ad", " we", "ly", "ee", " n", "id", " cl", "ac", "il", "</", "rt", " wi", "div", "e, ", " it", "whi", " ma", "ge", "x", "&#x0", "\'>", "=\'"];

var cb = rc.reduce(function(result, item, index, array) {
    result[item] = index;
    return result;
}, {})

var smaz = module.exports = {
  codebook: cb,
  reverse_codebook: rc,
  flush_verbatim: function(verbatim) {
    var output = [];
    if (verbatim.length > 1) {
      output.push(255);
      output.push(verbatim.length-1);
    } else {
      output.push(254);
    }
    var k = 0;
    for (; k < verbatim.length; k++) {
      output.push(verbatim.charCodeAt(k));
    }
    return output;
  },

  compress: function(input) {
    var verbatim = "";
    var output = [];
    var input_index = 0;

    while (input_index < input.length) {
      // Try to lookup substrings into the hash table, starting from the
      // longer to the shorter substrings
      var encoded = false;
      var j = 7;

      if (input.length-input_index < 7) {
        j = input.length-input_index;
      }

      for (; j > 0; j--) {
        var code = smaz.codebook[input.substr(input_index,j)];
        if (code != undefined) {
          // Match found in the hash table,
          // Flush verbatim bytes if needed
          if (verbatim) {
            output = output.concat(smaz.flush_verbatim(verbatim));
            verbatim = "";
          }
          // Emit the byte
          output.push(code);

          input_index += j;

          encoded = true;
          break;
        }
      }
      if (!encoded) {
        // Match not found - add the byte to the verbatim buffer
        verbatim += input[input_index];
        input_index++;

        // Flush if we reached the verbatim bytes length limit
        if (verbatim.length == 256) {
          output = output.concat(smaz.flush_verbatim(verbatim));
          verbatim = "";
        }
      }
    }
    // Flush verbatim bytes if needed
    if (verbatim) {
      output = output.concat(smaz.flush_verbatim(verbatim));
      verbatim = "";
    }
    return new Uint8Array(output);
  },

  decompress: function(input) {
    var output = "";
    var i = 0;
    while (i < input.length) {
      if (input[i] === 254) {
        // Verbatim byte
        if (i+1 >= input.length) {
          throw "Malformed smaz.";
        }
        output += String.fromCharCode(input[i+1]);
        i += 2;
      } else if(input[i] === 255) {
        // Verbatim string
        var j;
        if (i+input[i+1]+2 >= input.length) {
          throw "Malformed smaz.";
        }
        for (j = 0; j < input[i+1]+1; j++) {
          output += String.fromCharCode(input[i+2+j]);
        }
        i += 3+input[i+1];
      } else {
        // Codebook entry
        output += smaz.reverse_codebook[input[i]];
        i++;
      }
    }
    return output;
  }
};